JPH07270207A - Vibration-type measuring apparatus - Google Patents

Abstract

PURPOSE:To weld cap members accurately to the main body of a casing, wherein a sensor tube is contained, and to separate the cap members readily from the main body of the casing. CONSTITUTION:A mass flowmeter 1 is formed by inserting a pipe line 3, wherein fluid to be measured passes, in a tightly sealed casing 2. The casing 2 comprises a cylindrical casing main body 13 and disk-shaped cap members 14 and 15, which are coupled with both end openings 13a and 13b of the casing main body 13 so as to close the openings. A containing chamber 16 in the casing 2 has a tightly sealed structure, whose inside is closed with the cap members 14 and 15. The condensation of dew on the surface of the pipe line 3 is prevented. Protruding parts 13c and 13d forming the openings 13a and 13b protrude in the axial direction at both ends of the casing main body 13. The protruding parts 13c and 13d are thinner than the casing main body 13 and can be readily cut in the inspection or in repairing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration type measuring device,
In particular, it relates to improvement of a welded structure of a casing in which a sensor tube is housed.

[0002]

2. Description of the Related Art As a vibration type measuring device for measuring a physical quantity of a fluid by vibrating a pipe line to which the fluid is supplied, there is, for example, a Coriolis mass flow meter or a vibrating density meter.

In this Coriolis mass flowmeter, a sensor tube through which a fluid to be measured passes is vibrated in a radial direction by a vibrator, and a displacement of the sensor tube due to a Coriolis force proportional to the flow rate is detected by a pickup. There is. The vibrating density meter also has the same structure as the Coriolis mass flow meter, and the sensor tube vibrates at a frequency according to the density of the fluid to be measured.

The sensor tube, the vibrator, and the pickup are housed in a closed casing so as not to be affected by the surroundings. Further, if dew condensation occurs on the surface of the sensor tube, the natural frequency fluctuates. Since the measurement accuracy decreases, the inside of the casing is filled with dry protective gas to prevent dew condensation.

A conventional casing has, for example, a cylindrical casing body, and a disk-shaped lid member fitted into openings at both ends of the casing body. The casing body is made of iron pipe, and has the above-mentioned sensor tube, vibrator, and
A storage chamber in which the pickup is inserted is formed.

Further, the lid member has a through hole for allowing a conduit communicating with the sensor tube to penetrate therethrough at its central portion, and its outer periphery is machined to a size fit into the opening of the casing body. Then, in a state where the lid member is fitted in the opening of the casing body, the opening end portion and the outer periphery of the lid member are fillet-welded.

[0007]

However, when welding the opening of the casing body and the outer periphery of the lid member as described above, the lid member is easily affected by heat during welding. Thermal strain may occur and residual stress may occur in the sensor tube. When such distortion due to welding occurs in the sensor tube, the vibration characteristics of the sensor tube change.

This is because the amount of heat input when welding the opening of the casing body and the outer circumference of the lid member is not constant over the entire circumference. That is, when the amount of heat input is large in a part of the outer periphery of the lid member and the amount of heat input is small in the other part, a phenomenon occurs in which the conduit is pulled toward the part having a large amount of heat input.

Moreover, even if welding is performed using an automatic welding machine, it is difficult to make the amount of heat input by welding uniform, and it is difficult for even a skilled worker to eliminate welding distortion.

Furthermore, when inspecting or repairing the vibrator, pickup, etc. housed in the casing, the casing must be cut, which not only requires large maintenance work, but also takes time for inspection and repair. There is a problem such as.

Moreover, after the inspection and repair are completed, the casing must be welded again, and at that time, the lid member and the casing body cannot be centered, which may deteriorate the measurement performance after reassembly. .

Therefore, an object of the present invention is to provide a vibration type measuring device which solves the above problems.

[0013]

According to the present invention, a sensor tube for guiding a fluid to be measured supplied from the inflow pipe to the outflow pipe in a casing having an inflow pipe and an outflow pipe, and the sensor tube are provided. In a vibration type measuring device that stores a vibrating vibrator and a pickup that detects displacement of the sensor tube, the casing has an opening at both ends, and a storage chamber in which the sensor tube is inserted. And a lid member that is provided with the inflow pipe or the outflow pipe and closes the opening of the casing body, and the lid member is a plate-shaped lid body, and the lid body. And a fitting portion projecting in the axial direction from the end portion of the casing main body, and an end portion of the fitting portion is welded and fixed.

[0014]

The fitting portion extending in the axial direction is provided on the peripheral portion of the lid member, and the fitting portion is fitted into the opening of the casing body, and the opening end portion of the casing body and the end portion of the fitting portion are connected to each other. Since the gaps are welded, the welded portion can be formed at a position separated from the through hole through which the pipeline passes, and the influence of thermal strain on the sensor tube can be reduced. Furthermore, when inspecting or repairing the shaker, pickup, etc. inside the casing, the casing can be disassembled by cutting the opening end of the casing body and the end of the fitting part, facilitating inspection and repair work. In addition, the centering can be performed only by fitting the fitting portion of the lid member into the opening of the casing body during assembly.

[0015]

1 to 3 show a Coriolis mass flowmeter as an embodiment of a vibration measuring apparatus according to the present invention.

As the vibration type measuring device, there are a Coriolis type mass flowmeter and a vibration type density meter. Since the Coriolis mass flowmeter has substantially the same configuration as the vibration density meter, the mass flowmeter will be described in detail in this embodiment.

In each of the drawings, a mass flowmeter 1 is constructed by inserting a pipe 3 through which a fluid to be measured passes in a closed casing 2.
The pipe line 3 includes bellows 4A and 4B that are axially displaceable,
Inflow pipe 5, inflow side manifold 6, a pair of sensor tubes 7, 8, outflow side manifold 9, and outflow pipe 10.
It is formed by and.

The pair of sensor tubes 7 and 8 are straight stainless steel pipes extending linearly in the fluid flow direction (X direction), and are parallel to each other between the inflow side manifold 6 and the outflow side manifold 9. It is provided.

Support plates 11 and 12 through which the sensor tubes 7 and 8 are fixed are laterally provided near both ends of the sensor tubes 7 and 8. Therefore, the sensor tubes 7 and 8 are supported in parallel by the support plates 11 and 12 at both ends.

The casing 2 has a cylindrical casing body 13 and openings 13a and 13b at both ends of the casing body 13.
It is composed of disc-shaped lid members 14 and 15 which are fitted to the lid to close the lid. The casing 2 has a housing main body 13 having a storage chamber 16 for storing the bellows 4A and 4B, the inflow side manifold 6, the sensor tubes 7 and 8, and the outflow side manifold 9.

Therefore, the storage chamber 16 in the casing 2 is
It has a closed structure in which the inside is closed by the lid members 14 and 15, and it is possible to prevent dew condensation on the surface of the conduit 3 inserted into the storage chamber 16. Further, the closed storage chamber 16 is filled with a dry protective gas (for example, argon gas) at a predetermined pressure, and dew condensation may occur on the surfaces of the sensor tubes 7 and 8 to lower the measurement accuracy. To be prevented.

Therefore, due to dew condensation, the sensor tube 7,
Since the vibration characteristics (mainly the natural frequency) of No. 8 are prevented from fluctuating, the mass flowmeter 1 can measure the flow rate without trouble even in a high humidity atmosphere.

The casing body 13 is made of an iron pipe, and the both end openings 13a and 13b are machined so as to maintain a predetermined dimensional tolerance with respect to the outer circumferences of the lid members 14 and 15 in order to improve the centering accuracy. Has been done.

Furthermore, at both ends of the casing body 13,
The projecting portions 13c and 13d forming the openings 13a and 13b project in the axial direction. The protrusions 13c and 13d are
It is thinner than the casing body 13, and can be easily cut when performing inspection or repair as described later.

As shown in FIG. 2, the lid member 14 for closing the one opening 13a of the casing body 13 is the opening 1
Flat plate part (lid body) 14a for closing 3a, and flat plate part 1
4a, a bearing portion 14b having a through hole through which the straight pipe portion 4A ₁ of the bellows 4A penetrates, and a fitting portion 14c that axially projects from the peripheral edge of the flat plate portion 14a and fits into the opening 13a. Have.

Then, the protruding portion 13 of the casing body 13
c and the fitting portion 14c of the lid member 14 are joined by welding A, and the bearing portion 14b of the lid member 14 and the straight pipe portion 4A _{1 of the} bellows 4A are joined by welding B. Thus, the opening 13a is sealed by the lid member 14.

As shown in FIG. 3, the lid member 15 for closing the other opening 13b of the casing main body 13 has the same structure as the lid member 14 described above, but after the welding of the lid member 14 is completed, the casing is formed. Since it is welded to the opening 13b of the main body 13, it is difficult to fit the casing main body 13 without rattling when trying to secure a fit with the opening 13b.

Therefore, in the present embodiment, the outer periphery of the fitting portion 15c of the lid member 15 is cut to reduce the diameter and
The inner circumference of the opening 13b is cut to increase the diameter. And
A ring 23 having a small fitting tolerance is inserted or press-fitted into the annular gap S formed by the fitting portion 15c and the opening 13b.

Then, with the ring 23 inserted between the opening 13b and the fitting portion 15c, the ends of the opening 13b and the fitting portion 15c protruding in the axial direction from the flat plate portion 15a are joined by welding D. It As a result, the opening 13b and the fitting portion 15c are joined together without rattling, so that the lid member 15 is accurately centered.

Therefore, the opening 13b is closed by the lid member 15. In place of the ring 23, a plurality of spacers having the same thickness are provided in the opening 13b and the fitting portion 15c.
You may make it insert in the clearance gap S between them.

The casing 2 configured as described above protects the pipe line 3 and also functions as a support member for supporting the pipe line 3. Therefore, if the lid members 14 and 15 are not centered accurately, unnecessary stress acts on the sensor tubes 7 and 8 and causes a decrease in measurement accuracy.

Returning to FIG. 1, the description will be continued. The inflow pipe 5
Has a flange 5a connected to an upstream pipe (not shown) at the inflow end, and the other end of the inflow pipe 5 extends through the lid member 14 of the casing 2 to the inside of the casing 2. There is.

The upstream side of the inflow side manifold 6 is connected and fixed to the bellows 4A, and the downstream side is connected to the sensor tubes 7 and 8.
Is fixedly connected to the upstream end of the.

The outflow-side manifold 9 has its upstream side connected to the downstream ends of the sensor tubes 7 and 8, and its downstream side connected to the upstream ends of the bellows 4B.

The upstream end of the outflow pipe 10 is connected and fixed to the outflow manifold 9, and the downstream end thereof penetrates the lid member 15 of the casing 2 and projects downstream (X direction). A flange 10a connected to a downstream pipe (not shown) is provided at the downstream end of the outflow pipe 10.

The bellows 4A on the upstream side has a structure capable of expanding and contracting in the axial direction and absorbs only the expansion and contraction of the sensor tubes 7 and 8 in the longitudinal direction when the sensor tubes 7 and 8 are thermally expanded or contracted. Therefore, the inlet side manifold 6 is provided between the lid member 14 of the casing 2 and the inlet side manifold 6.
An anti-vibration mechanism 17 is provided to support so as not to vibrate.

The vibration-proof mechanism 17 has a plurality of columns 1 having one end fixed to the lid member 14 and the other end extending into the casing 2.
7a, and a metal diaphragm 17b that is connected across the other ends of the plurality of columns 17a and is connected to the inflow side manifold 6. Therefore, the inflow-side manifold 6 is supported by the anti-vibration mechanism 17 so as to be movable in the axial direction, and its lateral movement is restricted.

Further, the downstream side bellows 4B has an expandable and contractable structure similarly to the upstream side bellows 4A, and when the sensor tubes 7 and 8 are thermally expanded or contracted, the expansion and contraction of the sensor tubes 7 and 8 in the longitudinal direction is absorbed. To do. Therefore, between the side wall 2c of the casing 2 and the outflow side manifold 9,
An anti-vibration mechanism 18 is provided to support the inflow-side manifold 9 so as not to vibrate.

The vibration-proof mechanism 18 has a plurality of support columns 1 having one end fixed to the lid member 15 and the other end extending into the casing 2.
8a, and a metal diaphragm 18b that is horizontally connected between the other ends of the plurality of columns 18a and is coupled to the outflow-side manifold 9. Therefore, the outflow-side manifold 9 is supported by the anti-vibration mechanism 18 so as to be movable in the axial direction, and its lateral movement is restricted.

Reference numeral 19 denotes a vibration exciter, which has a structure similar to that of a substantially electromagnetic solenoid in which a coil and a magnet are opposed to each other, and is provided between the pair of sensor tubes 7 and 8 at substantially intermediate portions thereof.

Reference numeral 20 denotes an upstream pickup, which is arranged so as to be located upstream of the vibration unit 19. 21
Is a downstream pickup, and is arranged so as to be located downstream of the vibration unit 19. Each of the above pickups 2
Reference numerals 0 and 21 respectively have the same configuration as the electromagnetic solenoid, and detect the displacement of the sensor tubes 7 and 8 excited by the exciter 19.

The vibrator 19 and the pickups 20 and 2
Since 1 is stored in the storage chamber 16 of the casing main body 13 which is closed by the lid members 14 and 15, the flow rate can be measured without being affected by the outside.

When measuring the flow rate, the mass flowmeter 1 having the above configuration.
In, the pair of sensor tubes 7 and 8 are vibrated by the vibration exciter 19 in the direction toward and away from each other (Y direction). The fluid to be measured supplied from the upstream pipe (not shown) is the inflow pipe 5
It reaches the manifold 6 through the bellows 4A on the more upstream side, further passes through the flow path of the manifold 6, and flows into the vibrating sensor tubes 7 and 8. Then, the fluid that has passed through the sensor tubes 7 and 8 passes through the bellows 4B on the downstream side of the flow path of the manifold 9, and flows out from the outflow pipe 10 to a downstream side pipe (not shown).

In this way, the vibrating sensor tube 7,
When the fluid flows to 8, a Coriolis force having a magnitude corresponding to the flow rate is generated. Therefore, an operation delay occurs between the inflow side and the outflow side of the straight tubular sensor tubes 7 and 8, which causes a phase difference between the output signal of the upstream pickup 20 and the output signal of the downstream pickup 21.

Since the phase difference between the inflow side and the outflow side is proportional to the flow rate, the flow rate measurement control circuit 22 determines the flow rate based on the phase difference between the output signal from the pickup 20 and the output signal from the pickup 21. Calculate

Now, an assembly process for attaching the lid member 14 to the casing body 13 will be described.

First, the bellows 4A, 4B, the sensor tubes 7, 8, the manifolds 6, 9, the vibrator 19, the pickups 20, 21 are assembled.

Then, the straight pipe portion 4A ₁ of the bellows 4A is inserted through the bearing portion 14b of the lid member 14, and the lid member 14 and the bellows 4A are joined by welding B, and the bearing portion 14b and the straight pipe portion 4A are joined together. There is no gap between ₁ and it.
Then, the inflow pipe 5 is attached to the end of the straight pipe portion 4A ₁ of the bellows 4A.
Are joined by welding C.

Next, the assembly of the bellows 4A and 4B, the sensor tubes 7 and 8, the manifolds 6 and 9, the vibration exciter 19 and the pickups 20 and 21 is inserted into the casing body 13, and the fitting portion of the lid member 14 is inserted. 14c to the casing body 13
It is fitted in the opening 13a. And the casing body 1
The protruding portion 13c of No. 3 and the fitting portion 14c of the lid member 14 are joined by welding A. With this, the opening 13 a of the casing body 13 is sealed by the lid member 14.

As described above, the welds A and B are both flat plate portions 1.
Since it is located at a position projecting in the axial direction from 4a, heat at the time of welding is hard to be transmitted to the flat plate portion 14a of the lid member 14, and welding distortion is less likely to occur in the lid member 14 by that amount. Therefore, due to the welding A and B of the lid member 14, no residual stress is generated in the sensor tubes 7 and 8, and the deterioration of measurement accuracy is prevented. Further, since the welds A and B are provided with beads or grooves, the heat capacity of the welding heat is kept relatively low, and the thermal strain generated in the straight pipe portion 4A ₁ of the lid member 14 and the bellows 4A. Can be made smaller.

Further, by cutting the opening 13a of the casing body 13 in advance, as described above, the bellows 4A is formed.
The lid member 14 that supports the sensor tubes 7 and 8 is accurately centered via the, and the sensor tubes 7 and 8 are prevented from being displaced in the radial direction with respect to the center line of the casing 2.

As described above, in the cover member 15 on the outflow side, the ring 23 is inserted into the annular gap S formed between the fitting portion 15c and the opening 13b, and the fitting portion 1 is welded D.
The connection between 5c and the opening 13b is made. As a result, the welding D is located at a position projecting in the axial direction from the flat plate portion 15a of the lid member 15, so that heat generated during welding is applied to the flat plate portion 1 of the lid member 15.
5a, and welding distortion is less likely to occur in the lid member 15 by that amount. Therefore, due to the welding D of the lid member 15, no residual stress is generated in the sensor tubes 7 and 8, and a decrease in measurement accuracy is prevented.

Moreover, since the opening 13b and the fitting portion 15c are joined by the ring 23 without rattling, the lid member 15 is accurately centered. for that reason,
The sensor tubes 7 and 8 are covered with the casing 2 by the lid member 15.
The radial deviation with respect to the center line of the is prevented.

After assembly, the vibrator 19 and the pickup 2
When checking or repairing 0, 21, etc., the lid member 14 can be easily separated from the casing body 13 by cutting the weld A portion as shown in FIG.
That is, the middle portion of the projecting portion 13c that projects axially from the end of the casing body 13 is cut from the outer periphery.

As a result, the casing 2 is easily disassembled, so that the above inspection or repair can be performed in a short time.

Further, when the casing 2 is assembled again, the protrusion 13c remaining after cutting and the remaining portion of the fitting portion 14c of the lid member 14 are welded together, so that the lid member 14 can be easily attached. The lid member 14 can be joined to the lid member 13, and the lid member 14 can be accurately centered.

[0057]

As described above, according to the present invention, a fitting portion extending in the axial direction is provided on the peripheral portion of the lid member, and the fitting portion is fitted into the opening of the casing main body, Since the opening end and the end of the fitting part are welded, the welded part will be provided at a position separated from the through hole through which the conduit passes, and the effect of thermal strain on the sensor tube will be reduced. You can Furthermore, by cutting the opening end of the casing body and the end of the fitting part, the casing can be easily disassembled, and the vibrator and pickup in the casing can be inspected and repaired in a short time. . Further, since the centering can be performed only by fitting the fitting portion of the lid member into the opening of the casing body during assembly, it is possible to prevent the sensor tube from being displaced with respect to the casing after assembly.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a mass flowmeter to which an embodiment of a vibration measuring device according to the present invention is applied.

FIG. 2 is an enlarged vertical sectional view showing one assembly structure of a casing.

FIG. 3 is an enlarged vertical sectional view showing the other assembly structure of the casing.

FIG. 4 is a vertical sectional view for explaining an operation of separating the lid member and the casing body.

[Explanation of symbols]

 1 Mass flowmeter 6 Inflow side manifold 7, 8 Sensor tube 9 Outflow side manifold 11, 12 Support plate 13 Casing body 14, 15 Lid member 19 Vibrator 20 Upstream side pickup 21 Downstream side pickup 22 Flow rate measurement control circuit 23 Ring

Claims (1)

[Claims] 1. A sensor tube for guiding a fluid to be measured supplied from the inflow pipe to the outflow pipe in a casing provided with an inflow pipe and an outflow pipe, and a vibrator for vibrating the sensor tube, A vibration-type measuring device comprising: a pickup that detects displacement of a sensor tube; and a casing main body having an accommodation chamber in which both ends are open and the sensor tube is inserted, A lid member which is provided with a pipe or an outflow pipe and closes the opening of the casing body, and the lid member is a plate-shaped lid body, and a fitting protruding in the axial direction from the lid body. A vibration measuring device, wherein an opening end of the casing body and an end of the fitting part are fixed by welding.